Unlike the body’s inflammatory response to cuts and sprains,
with widespread swelling and stiffness immobilizing the injured area until it heals, the body’s response to sunburn is more localized and resulting in a distinct line dividing affected and unaffected areas of the skin.
Option Elimination -
(A) with widespread swelling and stiffness immobilizing the injured area until it heals, the body’s response to sunburn is more localized and resulting - "and" demand parallelism. "more localized" is ok, but "more resulting" is not ok. Moreover, "is resulting" is present continuous as in it is happening now while the intent is to state the general fact for which the simple present is preferable.
(B) where the injured area is immobilized with widespread swelling and stiffness until it has healed, sunburn generates a more localized response in the body, which results instead - "Unlike the body’s inflammatory response" is compared with "sunburn" - wrong.
(C) with the injured area immobilized by means of widespread swelling and stiffness until healing, sunburn generates a more localized response in the body, one resulting - same comparison issue as B.
(D) in which widespread swelling and stiffness immobilize the injured area until it has healed, the body’s more localized response to sunburn results - ok.
"Until" is used to indicate the point in time when an action or event will stop or a condition will be met. It suggests that something will continue to happen or remain true up to a specific time or event. Example 1: "I will wait here until you come back." In this sentence, the action of waiting will continue until the person returns. As soon as the person returns, the waiting will stop.
(E) in which widespread swelling and stiffness immobilize the injured area until healing, instead, the body’s more localized response to sunburn results - We already have the contrast "Unlike X, Y." why do we need another contrast using "instead" - redundant? Yes. Also, there is another mess up. To complete these two idioms, we need Unline X, Y. Also, A instead of B. So here is an incomplete contrast. We have, Unlike X, Instead B. Wrong.